Building automation systems or building control systems are systems that regulate, monitor and/or control various aspects of building operation and environment. Common examples of building automation systems include heating, ventilation and air conditioning (“HVAC”) systems, fire safety systems, and security systems. Residential spaces typically have relatively simple HVAC, fire safety and/or security systems, while large commercial or industrial properties can have thousands of elements, layers of control devices, and extensive communication networks and layers.
One of the major operations of an HVAC system or similar building automation system is to sense media and control aspects of the mechanical building structures based on the sensed properties of the media. For example, the sensed media in a room or other occupied space is the air. In a typical case, the air temperature in a room is sensed for the purposes of determining whether more or less chilled air should be admitted to the room in order to achieve a desired temperatures. The air may also be provided to a sensor for the purpose of determining the CO2, CO, or volatile organic compounds are present for the purposes of determining ventilation needs. Humidity and other aspects of the ambient air may also be sensed. In any event, the building automation system can control the operation of ventilation dampers, heating or cooling coils, and/or air handling units on the basis of such sensor data.
To perform the media sensing in building automation systems, it is known mount sensor units on the wall. These so-called wall sensors may or may not be combined with a control mechanism, such as is the case with a home thermostat. By contrast, in large commercial building automation systems, it is more likely that the sensor has the sole purpose of sensing media.
One of the issues regarding wall sensors in building automation systems relates to their bulk. Large boxy sensors typically do not match any décor within a room, and can sometimes even snag clothing, or injure a moving elbow or head. One desirable goal in the build automation system industry is to reduce the extent to which the sensor protrudes from the wall. The extent of protrusion from the wall is referred to herein as the “height”. However, there is a limit to how much the height of sensors may be reduced. In particular, as the wall sensors get thinner, it becomes more difficult to bring room air into the sensor housing for measurement by the sensing element. To this end, the air flow at or immediately adjacent to a wall surface is very low or even stagnant.
Accordingly, there is a tension between the desire to reduce the height (i.e. extension from the wall) of a sensor and the need for the height to allow for more air to flow to the sensor.